An aluminum nitride (AlN) crystal is known as a material having good thermal conductivity and excellent electrical insulating properties, and is therefore is being used as an insulating material requiring thermal conductivity, i.e. a thermally conductive and electrically insulating material. Specifically, a thermally conductive and electrically insulating material is used, for example, as a heat sink of a semiconductor circuit.
As for the AlN crystal, an AlN sintered body obtained by shaping AlN particles together with an appropriate binder and firing it, has been conventionally used (see, Unexamined Japanese Patent Publication No. 10-265267).
However, the AlN crystal comprising an AlN sintered body has had a problem that thermal conductivity is insufficient. In order to enhance thermal conductivity, a technique of blending metal particles or the like having excellent thermal conductivity in the sintered body has sometimes been employed, but in this case, the insulating property is impaired.